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Biomedical subjects

S Venkatesh

Publications and source records attributed to S Venkatesh.

68 records · Page 4Linked to original sources
PubMed1989

Neuropsychiatric manifestations of typhoid fever.

Neuropsychiatric manifestations of typhoid fever are not uncommon, occurring in 18 of 40 consecutive patients at the University Hospital of the West Indies. The clinical presentation ranges from a confusional state to hallucinations or meningism, and the diagnosis may be missed or unduly delayed unless there is a strong index of suspicion.

Adolescent↗
PubMed1986

An in-vitro morphological study of Q-switched neodymium/YAG laser trabeculotomy.

Laser trabeculotomies produced by directing a pulsed neodymium/YAG laser beam at specimens of human anterior chamber angle obtained post mortem or after enucleation were studied by light microscopy and by scanning and transmission electron microscopy to assess the dimensions of the openings created in the trabecular meshwork, their penetrance to the canal of Schlemm, and the extent or absence of laser induced cellular damage in immediately adjacent tissue. A pulse duration of 40-50 ns at energy levels of around 30 mJ was used and the laser cavity carefully tuned to give a Gaussian spatial mode pattern. Openings in the trabecular meshwork typically of 100 microns in diameter and penetrating through to the canal of Schlemm could be regularly created with only minimal damage to adjacent tissue as judged by transmission electron microscopy. The information so gained may be useful in determining the parameters required for successful laser trabeculotomy as a treatment for primary open-angle glaucoma.

Aged↗
PubMed1985

In vitro studies with a pulsed neodymium/YAG laser.

The relationships between the destructive effects of Q-switched Nd/YAG laser pulses and a number of experimental parameters were studied for various target materials including in particular excised, fixed samples of human trabecular meshwork. The laser parameters altered were the pulse energy, the convergence angle of the focused beam, and the position of the focus of the beam relative to the target's axial position. The main finding was that it was possible to make deep holes, of a diameter less than 100 micron, in virtually transparent samples of trabecular meshwork with a laser delivery system of 6 degrees convergence and pulse energies of 14 mJ or more. The relevance of this and the other experimental results to the development of a reliable system for performing internal trabeculotomies for the treatment of open-angle glaucoma is presented.

Cornea↗
PubMed1985

Thermal lens measurements in the cornea.

Q-switched pulses from a neodymium/YAG (yttrium-aluminium-garnet) laser were passed through corneal discs taken from the enucleated eyes of three baboons and four rabbits. The time course of heat dissipation following absorption of laser energy by the tissue was studied with the use of a second continuous wave laser beam acting as a probe. It was found that the absorption of each neodymium/YAG pulse created a transient divergent lens within the cornea as theoretical considerations predicted. The relaxation time that characterised the decay of this thermal lens for a 1/e laser beam diameter of 2.0 mm was found to be 2.3 +/- 0.1 s (mean +/- standard error for 12 separate groups of measurements). Our results show that Q-switched laser pulses passing through apparently unaffected transparent tissues can induce thermal lens effects which persist for several seconds. The optical transfer of each pulse in a stream will be identical only if enough time is left between pulses for the tissues to return to their initial state. Therefore, when such laser pulses sharply focused to perform high precision intraocular surgery are used, thermal lensing in the transparent ocular media must limit the rate at which pulses can be usefully delivered.

Animals↗
PubMed1981

Boundary-layer oxygen depletion in blood gas analysis.

When O2 is withdrawn from blood by diffusion through a membrane and an O2-depleted boundary layer is formed, it is suggested that the depletion can cause significant dissociation of oxyhemoglobin (HbO2) in this layer. The resulting nonlinear relation between net diffusive flux of O2 through the membrane and the blood PO2 should be observable with membrane systems having a sufficiently high permeability to O2. Evidence for this suggestion is presented from in vitro experiments using a mass spectrometer to analyze the O2 flux through membrane systems. A theoretical model of HbO2 dissociation in the depleted boundary layer of blood that explains these results qualitatively is developed to yield quantitative predictions found to be in reasonable agreement with the experimental observations. The effect was seen to be of significance for membrane systems with O2-sampling rates of about 2 X 10(-9) ml. s-1. Torr-1 and over; so if such systems are to be used for the analysis of blood PO2, the phenomenon must be taken into account.

Blood Gas Analysis↗
PubMed1977

Cranial isotopic section scanning.

Some results of isotopic cranial section scanning are presented from a busy neurosurgical practice. Isotopes have been used for parenchymal lesions and also CSF pathway imaging. Comparisons with information yielded by other neuroradiological techniques have indicated that tomographic sections are a worthwhile addition to rectilinear isotope scans. In particular comparison with X-ray transmission (EMI) scans has confirmed the anatomical accuracy of the method and the two techniques have proved complementary in patient management.

Brain↗
PubMedDate not supplied

Maternal care receptivity--an innovative approach for the evaluation of MCH services.

Despite rapid expansion in the maternal and child health and family planning services, there have been few attempts made to study the extent of utilisation of these services and their impact. The present study reports a simple method evolved in the quantification of utilisation of maternal care services (called maternal care receptivity - MCR), the relationship of factors such as age, parity, caste of the women and the distance of the health centre on the MCR and the impact of MCR on perinatal and neonatal mortalities. An inverse relationship was observed between MCR and perinatal and neonatal mortality rates and the two rates were three times less among babies born to mothers with high MCR scores compared to those with poor MCR scores.

Analysis of Variance↗
PubMedDate not supplied

SARS: the new challenge to international health and travel medicine.

Severe acute respiratory syndrome (SARS), the first severe new infectious disease of this millennium, caused widespread public disruption. By July 2003, 8427 probable SARS cases had been reported from 29 countries with a case fatality rate of 9.6%. The new febrile respiratory illness spread around the world along the routes of international air travel, with outbreaks concentrated in transportation hubs or densely populated areas. The etiologic agent was identified as a novel coronavirus, SARS-CoV. The disease is transmissible person-to-person through direct contact, large droplet contact and indirect contact from fomites and unwashed hands. Saudi Arabia successfully prevented the entry of the disease by imposing travel restrictions, special entry requirements, screening procedures at airports, including temperature checks, and quarantine. Ongoing efforts are aimed at developing case investigation, case management and surveillance protocols for SARS.

Aviation↗